Dynamic Random Access Memories (DRAMs) since the 64K generation have offered options to the basic memory function provided by a simple x1 organization. The 64K DRAM offered a 64Kx1 organization as well as a 16Kx4 organization at the same memory density. However, these two offerings were usually totally separate designs, mask sets and they required separate qualifications by customers. The 256K generation for the most part paralleled the 64K regarding having separate designs for the 256Kx1 and 64Kx4 parts. With the 256K additional options beside organization were offered. The 256K generation also offered nibble mode on the x1 along with the standard page mode version.
With the advent of the 1M, several manufacturers sourced all their device options from one basic mask set. The device options included choice of organization and choice of function, such as page, nibble or static column modes. The desired option is selected during wafer fabrication at metal patterning or in the assembly operation at wire bond. This approach simplifies the inventory of multiple device types for both manufacturer and customer.
In bond programming, the option desired is chosen by selectively bonding the programming pads to Vdd or Vss or leaving them open. If a pad is left un-bonded, the pad is taken to a default potential on chip. The necessary reconfiguration within the chip for the desired mode of operation is accomplished through setting of logic gates and use of CMOS transfer devices. Selection at this stage of manufacturing puts the decision closer to the point of customer delivery and allows the marketing and manufacturing organizations greater flexibility in servicing the customer's needs.
The use of bond programming leads to an interesting possibility--letting the customer himself determine the option he wants at the point of use, his board. If a way can be found for him to do so, without increasing the cost of the device or his system costs, then there appear to be advantages for both the manufacturer and the user. Having a single device from which to source all device options solves his inventory problems for multiple device types while freeing his designers to choose the best device for the application. In both cases it simplifies the question of product mix from "how many of which kind?" to simply "how many?"